Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
  • A61B1/06—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor with illuminating arrangements
  • A61B1/0605—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor with illuminating arrangements for spatially modulated illumination
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/0059—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence
  • A61B5/0082—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence adapted for particular medical purposes
  • A61B5/0084—Measuring for diagnostic purposes; Identification of persons using light, e.g. diagnosis by transillumination, diascopy, fluorescence adapted for particular medical purposes for introduction into the body, e.g. by catheters
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
  • A61B1/04—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor combined with photographic or television appliances
  • A61B1/05—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor combined with photographic or television appliances characterised by the image sensor, e.g. camera, being in the distal end portion
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
  • A61B1/06—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor with illuminating arrangements
  • A61B1/0615—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor with illuminating arrangements for radial illumination
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
  • A61B1/267—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor for the respiratory tract, e.g. laryngoscopes, bronchoscopes
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
  • A61B5/107—Measuring physical dimensions, e.g. size of the entire body or parts thereof
  • A61B5/1076—Measuring physical dimensions, e.g. size of the entire body or parts thereof for measuring dimensions inside body cavities, e.g. using catheters
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
  • A61B5/107—Measuring physical dimensions, e.g. size of the entire body or parts thereof
  • A61B5/1079—Measuring physical dimensions, e.g. size of the entire body or parts thereof using optical or photographic means
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/48—Other medical applications
  • A61B5/4806—Sleep evaluation
  • A61B5/4818—Sleep apnoea
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
  • A61B5/6846—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be brought in contact with an internal body part, i.e. invasive
  • A61B5/6847—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be brought in contact with an internal body part, i.e. invasive mounted on an invasive device
  • A61B5/6852—Catheters
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/12—Diagnosis using ultrasonic, sonic or infrasonic waves in body cavities or body tracts, e.g. by using catheters
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B8/00—Diagnosis using ultrasonic, sonic or infrasonic waves
  • A61B8/44—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device
  • A61B8/4483—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device characterised by features of the ultrasound transducer
  • A61B8/4494—Constructional features of the ultrasonic, sonic or infrasonic diagnostic device characterised by features of the ultrasound transducer characterised by the arrangement of the transducer elements
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
  • A61B2562/02—Details of sensors specially adapted for in-vivo measurements
  • A61B2562/0233—Special features of optical sensors or probes classified in A61B5/00
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
  • A61B2562/04—Arrangements of multiple sensors of the same type
  • A61B2562/043—Arrangements of multiple sensors of the same type in a linear array
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B2576/00—Medical imaging apparatus involving image processing or analysis
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/145—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue
  • A61B5/14542—Measuring characteristics of blood in vivo, e.g. gas concentration, pH value; Measuring characteristics of body fluids or tissues, e.g. interstitial fluid, cerebral tissue for measuring blood gases
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
  • A61B5/7271—Specific aspects of physiological measurement analysis
  • A61B5/7285—Specific aspects of physiological measurement analysis for synchronising or triggering a physiological measurement or image acquisition with a physiological event or waveform, e.g. an ECG signal

Definitions

• This invention relates to catheters which incorporate an optical sensor, and specifically but not limited to an upper airway catheter having an optical sensor for monitoring the shape of the upper airway in sleeping users.
• OSA Obstructive Sleep Apnoea
• OSA causes an intermittent cessation of airflow. When these obstructive episodes occur, an affected person will transiently arouse. As these arousal episodes typically occur 10 to 60 times per night, sleep fragmentation may produce excessive daytime sleepiness. It is known that some patients with OSA experience over 100 transient arousal episodes per hour. OSA may also lead to cardiovascular and pulmonary disease.
• CPAP Continuous Positive Airway Pressure
• OSA Obstructive Sleep Apnea
• PAP Positive Airway Pressure
• DISE drug induced sleep endoscopy
• ENT Ear, Nose and Throat
• Pressure catheters try to overcome some of the limitations associated with DISE, but upper airway manometry has shortcomings as well since it only identifies collapse location, but doesn't provide any information regarding the configuration and severity of the upper airway obstructions. Upper airway manometry also provides no visual confirmation in case of an event.
• Optical catheters and endoscopes have been proposed as a concept to quantify airways. Examples of optical endoscopes can be found from Muller et al "Noncontact three-dimensional laser measuring device for tracheoscopy", Annals of Otology, Rhinology and Laryngology, Vol.
• the typical optical catheter has an optical sensor which at best has a field of view which significantly limits the ability to monitor a substantial cross sectional area and therefore can miss or miss diagnose the type of event occurring in the airway as the optical catheter is 'directed' in a direction which fails to capture the event or capture the event significantly well.
• a catheter comprising:
• each optical sensor having a sensor length along a direction parallel to or at an angle of less than 45 degrees to the catheter direction, and each optical sensor comprising:
• a light generator configured to project at least one light output at a radial projection angle with respect to the catheter length onto the inner surface of the elongated volume into which the catheter is inserted; and an imaging device having a field of view with a central axis substantially parallel to or at an angle of less than 45 degrees to the catheter length, the imaging device configured to observe the at least one light output on the inner surface of the elongated volume.
• the angle is less than 30 degrees or less than 20 degrees.
• This catheter comprises multiple optical sensors along its length.
• the optical sensor is for example an elongate structure along the catheter, so that the sensor has an elongate axis direction which corresponds to the catheter length direction or is offset by a small amount from it.
• the imaging device field of view has a central axis substantially parallel to the length direction of the optical sensor, and the light generator is configured to project light radially with respect to the length direction of the optical sensor.
• the sensor axis and field of view central axis of the imaging device may correspond exactly to the sensor length direction. This defines a forward illumination and forward looking image sensor, and the imaged surface is a perpendicular ring. However, there may be a deliberate offset angle so that the imaged surface is a slice which is not perpendicular to the catheter length.
• the light generator may generate a light output in the form of a light pattern, and may thus be described as a structured light source or light pattern generator.
• the pattern for example has at least one narrow peak in intensity along the catheter direction. This peak may be continuous around the full radial direction (i.e. an annular ring) or it may be discontinuous around the radial direction (i.e. a set of spots). The intensity preferably drops as close to zero as possible each side of the narrow peak.
• This arrangement thus enables a catheter to be used to make measurements while the catheter is static or stationary within the volume (such as an upper airway) for more than a single substantial cross sectional region, or partial cross section and thus allows a more realistic analysis of the volume to be made without the need to move the catheter or endoscope within the volume.
• the arrangement enables a compact optical design which can fit within the catheter.
• Each optical sensor is preferably arranged to receive an image of the complete cross section, so that only one image sensor is needed at each location where images are to be taken.
• the imaging devices may face forward or backward and this means they can be provided locally at the site of the cross section to be imaged. Electrical signals rather than optical signals can be routed along the catheter from the multiple sensors.
• the field of view of the imaging device may include the inner surface of the elongate volume because it has a sufficient range of angles of incidence away from the catheter length axis, or else it may have a narrower range of angles of incidence, but the light from the inner surface of the elongated volume is redirected (e.g. reflected) to fall within the field of view of the imaging device.
• the central axis of the imaging device is in each case aligned with (or slightly offset from the direction of) the catheter, which means it can more easily fit into the confined and limited space of the catheter. It also means a single imaging device can receive light in a uniform manner from all radial directions.
• the light pattern generator may comprise a light source for generating a light beam in a direction parallel to the catheter direction, and a light redirection element configured to redirect the light beam to generate the at least one light pattern at an oblique and/or right angle to the catheter length.
• the light pattern generator light beam may be aligned with a central axis of the catheter, and the imaging device has a field of view with a central axis aligned with a central axis of the catheter.
• the imaging device and the light source may be centrally positioned within the catheter.
• the light pattern generator light beam may be offset from a central axis of the catheter, and the imaging device has a field of view with a central axis aligned with the central axis of the catheter.
• the light source is offset from the central axis, and the reflective element is accordingly also offset from the central axis. This enables the components to be arranged in a more compact way.
• the light pattern generator may further comprise: a lens configured to provide a coUimated or partially coUimated light beam substantially aligned along the catheter length; and a reflective element configured to reflect the light beam to generate the at least one light pattern at an oblique and/or right angle to the catheter length.
• the length of the sensor can be shortened as the reflective element may convert an axial light pattern into a radial light pattern.
• a sensor is specifically able to operate within and/or along a catheter as the generation of the at least one light pattern at a radial projection prevents a proximal or distal part of the catheter from shadowing the sensors operation.
• the reflective element of the light pattern generator may comprise a reflective cone comprising a single reflective surface angle configured to generate the at least one light pattern in the form of a ring at an oblique and/or right angle to the catheter length.
• the reflective cone may convert an axial light pattern into a radial light pattern where the beam is reflected to form a ring pattern which can be reflected onto the inner surface of the elongated volume.
• the reflective element may comprise a reflective cone comprising a stepped reflective profile having at least two different reflective surface angles and configured to generate at least two light patterns in the form of at least two rings at an oblique and/or right angle to the catheter length.
• the reflective element may comprise a reflective cone comprising a varying reflective surface angle and configured to generate a distributed light pattern at an oblique and/or right angle to the catheter length.
• the detection and determination of the cross sectional profile of the volume may be assisted.
• the reflective element may comprise a diffractive optical element within the optical pathway of the light beam either before or after a reflective cone configured to generate the at least one light pattern at an oblique and/or right angle to the catheter length based on the diffractive optical element.
• the diffractive optical element enables the generation of a more sophisticated pattern, such as multiple rings, which may allow a more accurate cross sectional determination to occur.
• the reflective element may comprise a volume hologram within the optical pathway of the light beam configured to generate the at least one light pattern at an oblique and/or right angle to the catheter length based on the diffractive optical element.
• the imaging device may comprise a camera located on the side of and external to the catheter and directed along the direction of the light beam.
• the camera may capture images of the light pattern projected on the volume (airway) wall in a forwards (or axial) field of view.
• the imaging device may comprise a camera located within the catheter and directed along and substantially opposite the direction of the light beam.
• the camera may capture images of the light pattern projected on the volume (airway) wall in a forwards (or axial) field of view, but allows the diameter of the catheter sensor to be reduced as there is no 'stacking' of the components in a radial direction.
• the imaging device may comprise a camera and a reflective element located within the optical sensor and directed along and substantially opposite the direction of the light beam, the reflective element configured to refiect at least part of the field of view of the camera from an axial field of view direction to a radial field of view direction.
• the reflective element of the imaging device may comprise a reflective cone comprising a single reflective surface angle configured to reflect at least part of the field of view of the camera (1013) from an axial field of view direction to a radial field of view direction
• the camera may capture images of the light pattern projected on the volume (airway) wall in a sideways (or radial) field of view which assists in reducing the length of the sensor.
• the reflective element of the imaging device may comprise a reflective cone comprising a stepped reflective profile having at least two different reflective surface angles and configured to reflect a first part of the field of view of the camera from an axial field of view direction to a first range radial field of view directions, and a second range of the field of view of the camera from an axial field of view direction to a second range radial field of view directions non continuous with the first range radial field of view directions.
• the camera may capture images of the light pattern projected on the volume (airway) wall in a sideways (or radial) field of view which assists in reducing the length of the sensor but allows an overlapping field of view of the camera to assist in determining any erroneous images.
• the camera may capture images of the light pattern projected on the volume (airway) wall with a greater degree of coverage that would be provided by the original camera.
• the reflective element of the imaging device may comprise a reflective cone comprising a varying reflective surface angle and configured to generate a sensor field of view range less than the field of view of the camera.
• the camera may capture images of the light pattern projected on the inner wall of the volume (airway) with a smaller degree of coverage that would be provided by the original camera but with a greater density of imaging of the area that is covered.
• the light generator is an integral part of the imaging device, and generates a non-patterned light output with sufficient radial extent to illuminate the inner surface of the elongated volume into which the catheter is inserted, wherein the imaging device has a field of view with an acceptance angle sufficient to receive light directly from the illuminated inner surface of the elongated volume into which the catheter is inserted.
• This design avoids the need for a structured light source, by illuminating and imaging the inner surface of the conduit. Image analysis may then be used to interpret the findings.
• First and second optical sensors may face each other. This means images may be taken close together.
• the optical sensor may further comprise a transparent capillary configured to support the light pattern generator and the imaging device and further permit the transmission of the at least one light pattern from optical sensor to the inner surface of the volume.
• the transparent capillary may support and protect the pattern generator and imaging device from mechanical damage, and enable easy cleaning of the sensor.
• the optical sensor may further comprise at least one transparent rod, wherein the at least one transparent rod may comprise at least one of: a lens hole or hollow configured to receive a light guide and configured to operate as a lens configured to generate a light beam substantially aligned along the catheter length; a light pattern generator hole or hollow configured to reflect the light beam to generate the at least one light pattern; a field of view hole or hollow configured to reflect at least part of the field of view of the imaging device from an axial field of view direction to a radial field of view; an imaging device hole or hollow configured to receive the imaging device.
• the at least one transparent rod may comprise at least one of: a lens hole or hollow configured to receive a light guide and configured to operate as a lens configured to generate a light beam substantially aligned along the catheter length; a light pattern generator hole or hollow configured to reflect the light beam to generate the at least one light pattern; a field of view hole or hollow configured to reflect at least part of the field of view of the imaging device from an axial field of view direction to a radial field
• the transparent rod may support and protect the pattern generator and imaging device from mechanical damage, and enable easy cleaning of the sensor and furthermore provide a structure which reduces the number of optical interfaces and therefore reduces the number of parasitic reflections captured by the imaging device.
• the at least one transparent rod may comprise: a first transparent rod comprising the lens hole or hollow and light pattern generator hole or hollow; a second transparent rod comprising the field of view hole or hollow and the imaging device hole or hollow, wherein the first transparent rod and the second transparent rod are fixed together.
• the first transparent rod and the second transparent rod may be fixed together by glue.
• the optical sensor may be rigid member such that the optical distance between the light pattern generator and the imaging device is a defined length.
• the optical sensor may further comprise at least one conduit, the conduit may be further configured to locate within the sensor at least one light guide for at least one further optical sensor.
• the senor may be arranged with further sensors and provide a light source to sensors located at the distal end of a catheter arrangement.
• the optical sensor may further comprise at least one light source, the at least one light source may be optically coupled to the lens.
• the at least one light source may comprise at least one of: at least one light emitting diode; at least one laser diode; at least one vertical-external-cavity surface-emitting- laser.
• the optical sensor may further comprise at least one conduit, the conduit may be further configured to locate within the sensor at least one imaging device output from at least one further catheter sensor.
• the senor may be arranged with further sensors and provide a data pathway from sensors located at the distal end of a catheter arrangement.
• a catheter may comprise at least two optical sensors as described herein, the at least two optical sensors being distributed spaced along the catheter, and wherein the at least two optical sensors are configured to observe different substantial cross sections of a volume within which the catheter is located.
• an imaging method for obtaining images from at least two optical sensors distributed along a catheter wherein the sensors are configured to observe different cross sections of an elongated volume within which the catheter is located, each optical sensor having a sensor length along a direction parallel to, or at an angle of less than 45 degrees to, the catheter direction, the method comprising, for each optical sensor:
• the angle is less than 30 degrees or less than 20 degrees.
• Projecting at least one light output may comprise generating a light output substantially aligned along the sensor length; and reflecting the light beam to generate the at least one light output at an oblique and/or right angle to the sensor length.
• the catheter may include a transparent capillary.
• the at least one light source may comprise at least one of: at least one light emitting diode; at least one laser diode; at least one vertical-external-cavity surface-emitting- laser.
• a conduit may be provided within or on the optical sensor, the conduit locating at least one of: at least one light guide for at least one further optical sensor; and at least one imaging device output from at least one further catheter sensor.
• the volume may be an upper airway volume.
• the substantial cross sections of diagnostic interest within the volume may be the velum, oropharynx, base of tongue and epiglottis.
• Figure 1 shows a typical upper airway and example cross sections
• Figure 2 shows a first example of an upper airway catheter according to some embodiments
• Figure 3 shows a detail of the first example of an upper airway catheter according to some embodiments
• Figure 4 shows the first example upper airway catheter sensor configuration as shown in Figure 2 and 3 according to some embodiments
• Figures 5 shows a upper airway monitoring system incorporating an upper airway catheter as shown in Figures 2 to 4 and a data processing unit according to some embodiments;
• Figure 6 shows an example of a collapse event as monitored by the upper airway monitoring system shown in Figure 5
• Figure 7 shows an example ultrasonic sensor as implemented on the upper airway catheter as shown in Figures 2 to 4 according to some embodiments;
• Figure 8 shows a first example optical sensor as implemented on the upper airway catheter as shown in Figures 2 to 4 according to some embodiments;
• Figure 9 shows a second example optical sensor as implemented on the upper airway catheter as shown in Figures 2 to 4 according to some embodiments;
• Figure 10 shows an alternative way to convert an axial illumination pattern to a radial illumination pattern
• Figure 11 shows an example cross sectional dimension determination based on the second example optical sensor shown in Figure 9;
• Figure 12 shows a third example optical sensor as implemented on the upper airway catheter as shown in Figures 2 to 4 according to some embodiments;
• Figure 13 shows two examples of field of view reflection suitable for implementing in the third example optical sensor as shown in Figure 11 ;
• Figure 14 shows a fourth example optical sensor as implemented on the upper airway catheter as shown in Figures 2 to 4 according to some embodiments;
• Figure 15 shows examples of light patterns which are suitable for implemented in example optical sensors as shown in Figure 8 to 14 according to some embodiments;
• Figure 16 shows an example of a curved profile reflective element suitable for implementation in example optical sensors as shown in Figure 8 to 14 according to some embodiments;
• Figure 20 shows a third example of an upper airway catheter sensor configuration according to some embodiments.
• the UI may be configured to generate an accepted upper airway classification method like VOTE, or be configured to replay the recorded key events.
• the system may be integrated with other sensors (for example body position, oxygen saturation, sleep stage) or in some embodiments be used during a full polysomnography (PSG) study. In such a manner the system can provide correlations between airway geometry and sleep parameters, for example the dependence of obstructions patterns on sleep stage/position or which collapse patterns cause the strongest oxygen desaturation events.
• the individual sensors are optical (patterned light) sensors or ultrasound sensors to measure the airway cross section, as will be described below. A substantial cross section is one in which the majority of the cross section of the inserted volume is observed.
• the observation can in some embodiments be one of observing of a substantially continuous ring pattern (of light) on the volume interior wall.
• the substantial cross section coverage and range is provided directly by the observation.
• a substantial cross section range can be achieved in some embodiments
• a broken ring pattern (of light) being observed by a substantially continuous sensor, or a substantially continuous ring pattern (of light) observed by a non-continuous sensor or sensor array, or a broken ring pattern (of light) observed be a non-continuous sensor or sensor array but providing a substantial cross section range.
• the substantial coverage can be generated or determined by interpolation. For example where in some embodiments the gaps in observed coverage are small and/or regularly distributed these values can be 'filled in' or interpolated easily.
• the optical and/or other sensors can be configured to observe or visualize more than only this projected ring.
• the sensors can be configured to observe the substantial cross-section to provide more information about the surface of the inner airway wall.
• the sensor can be configured in some embodiments to provide a two-dimensional or area 'view' with a substantial cross-section. For example this could be provided by an array of neighboring rings and interpolating the space between them or by the optical sensor or another sensor (such as an ultrasound sensor) observing or imaging a two-dimensional area of substantial cross section range.
• the senor and in particular the optical sensor as described herein is configured to be located within and along the catheter.
• the optical sensor is configured to generate or project (by a light pattern generator) at least one light pattern at a radial projection angle to the (local) catheter length direction onto an inner surface of an elongated volume into which the optical sensor is inserted.
• a radial projection angle is possibly a right angle from the local catheter length direction but may also be any suitable oblique angle with respect to the local catheter length direction and preferably one within a right angle sector centered at the normal of the catheter length direction and therefore the sensor length direction.
• an example patient upper airway is shown with typical cross sections at designated locations within the upper airway.
• the patient 1 is shown with cross sections locations such as the Esophagus 3, Hypopharynx (or Laryngophyarynx or epiglottis) 5, Oropharynx (or base of tongue) 7, Velopharynx 9, Proximal nasopharynx 11 and Nasal cavity 13.
• the anterior-posterior direction in the example cross sections is the vertical, and the lateral direction is the horizontal.
• an upper airway catheter 103 is shown in location according to some embodiments (in other words the catheter 103 following insertion into the patient).
• the catheter 103 may in some embodiments
• embodiments be inserted through the patient's 1 nose until the caudal side is lodged in the esophagus.
• the insertion may be performed by a trained nurse or an ENT specialist in the evening or before a nap during the day.
• the anterior-posterior direction in the example cross sections is the vertical; and the lateral direction is the horizontal.
• the catheter 103 may comprise a multitude of sensors 104 configured to measure the cross section at the upper airway at (or near) defined structures or locations within the upper airway.
• these structures or locations to be observed and monitored may comprise the velum (or the soft palate) 5, the oropharynx 7, the base of the tongue 9 and the epiglottis 11.
• the catheter 103 may be flexible in that the whole length of the catheter 103 can move or bend. However it would be understood that in some embodiments the catheter 103 is configured to be semi- flexible in that parts or portions of the catheter 103 are flexible and other parts or portions of the catheter 103 are rigid or non- flexible, or be semi- flexible in that some dimensions of portions of the catheter 103 are flexible and some dimensions are fixed or rigid.
• Figure 3 shows an example catheter 103 comprising flexible non- sensing parts 105 located between rigid sensor 104 parts.
• the rigid sensor 104 parts of the catheter may then be configured to determine cross-sectional profiles 107 as defined by the upper airway walls 100.
• the catheter 103 may be steerable in that the flexible parts 105 or flexible catheter 103 can be actively directed during insertion.
• the catheter 103 may be passively directed during insertion in that it flexes or bends in response to coming into contact with the upper airway walls 100.
• 5 mm and may be less than or equal to 3mm in diameter.
• the location of the sensors 104 may be adaptable.
• the ENT specialist may configure the catheter 103 for each patient based on prior measurements.
• the spacing of the catheter 103 sensors 104 can be adjusted relative to each other.
• the catheter 103 may comprise telescopic or adjustable length parts or portions between the sensors to adjust the relative locations of the sensors 104.
• the sensors 104 themselves may be movable on the catheter 103 body.
• the catheter 103 as described here comprises a first or velum sensor 104g configured to be located within the velum 9 region of the patient's upper airway, a second or oropharynx sensor 104 7 configured to be located within the oropharynx 7 region of the patient's upper airway, a third or base of tongue sensor 104 6 configured to be located within the base of tongue 6 region of the patient's upper airway, and a fourth or epiglottis sensor 104 5 configured to be located within the epiglottis 5 region of the patient's upper airway.
• the catheter system 400 may in some embodiments comprise the catheter 103, such as shown in Figures 2 to 4, which may in some embodiments be connected to a data processing unit (DataPU) 401, and in some
• DataPU data processing unit
• the data processing unit 401 may comprise a processor 403 configured to receive the sensor 104 data and determine or generate suitable cross sectional information.
• the data processing unit 401 may furthermore comprise at least one memory 405, which in some embodiments may be sub-divided into program memory 407 configured to store instructions for operating or execution by the processor 403, for example programs or instructions for processing sensor data to determine the cross-sectional information or results.
• the at least one memory 405 may furthermore in some embodiments comprise data memory 409 configured to store data such as for example unprocessed sensor data.
• the data memory 409 may in some embodiments be configure to store processed data such as the cross sectional information determined by the processor 403 during the duration of the patients sleep.
• the data processing unit 401 may in some embodiments comprise a user interface (UI) 411.
• the user interface 411 may be any suitable user interface, for example a touch screen display configured to enable the display of data to the user of the system and also data input from the user.
• the user interface 411 may comprise separate data display and data input means.
• the data processing unit 401 may comprise a keyboard/keypad for entering data inputs and a display screen for displaying data to the ENT.
• the data processing unit 401 may be further configured to receive data from other sensors.
• the data processing unit may be configured to receive data from sensors such as body position, oxygen saturation, sleep stage.
• This other sensor data may further be time coded or synchronized with the catheter 103 based sensor 104 data such that the data processing unit 401 may be configured in some embodiments to determine and/or display any correlations between airway geometry and sleep parameters, for example the dependence of obstructions patterns on sleep stage/position or which collapse patterns cause the strongest oxygen desaturation events.
• the catheter 103 determines or generates an insertion depth measurement during the insertion and
• the data processing unit 401 may access data from additional sensor(s) to provide 'richer' event data, such as determining the type of collapse based on the sleep stage or a typical oxygen desaturation measurement for a type of collapse.
• the data processing unit 401 may generate or determine a '3D' model representing the change of the airway shape during any determined collapse events.
• the data processing unit 401 may furthermore enable the user of the system, for example the ENT, the ability to replay certain events.
• the data processing unit 401 can thus, in some embodiments, be configured to construct a model of the volume.
• the model of the volume may be generated based on the data provided by the sensors located on the catheter 103.
• the data processing unit 401 may furthermore be configured (based on the model of the volume or on the data provided by the sensors located on the catheter 103) to generate clinical information suitable for analysis by the ENT.
• the clinical information in some embodiments comprises determining at least one volume contraction or collapse.
• the data processing unit 401 can in some embodiment based on determining the at least one volume contraction or collapse be configured to generate further clinical information such as determining at least one of: the location of the at least one contraction or collapse; the degree (severity) of the at least one volume contraction or collapse; and the configuration of the at least one volume contraction or collapse.
• the data processing unit can be configured to sort the clinical information over a sub-period of time.
• a suitable sub-period of time may be a sleep state period and/or a sleep position period.
• the user interface as described herein can for example display the determined/stored/replayed clinical information.
• the user interface can be configured to display the clinical information in the form of the at least one volume collapse (and the associated characteristics or descriptors of the at least one volume collapse or contraction such as the location, the degree (severity), and the configuration of the at least one volume collapse or contraction) can be displayed.
• the sensor 104 for such an airway catheter 103 faces a number of constraints that require significant design skill in order to achieve a successful result.
• the sensor length has to be limited to ensure passage of the sensor through the nose.
• any sensor 104 connections to the outside are configured to be small enough not to conflict with or interfere with other sensors 104.
• the senor 104 is configured to be encapsulated, and therefore easily cleanable. Similarly the sensor 104 is configured in some embodiments such that a thin coat of saliva or slime should not prevent the sensor from functioning or from producing inaccurate data.
• the sensor 104 in some embodiments is configured to operate at a rate fast enough to detect a collapse. Similarly in some embodiments the sensor 104 is configured to operate at a rate fast enough to detect (and enable the data processing unit 401 in some embodiments to filter out) other movements of the airway, such as for example breathing motion.
• the sensor 104 in some embodiments is configured to operate without the need for mechanical scanning or movement. This is because any movement of (or inside) the catheter 103 can keep the patient from falling asleep or wake the patient up and because mechanical arrangements tend to make a sensor fragile.
• the sensor configured to measure the cross sectional dimension of the airway is at least one or an array of ultrasound transducers 604 arranged around the catheter 103.
• the ultrasound transducer 604 may be, in some embodiments, 'small' ultrasound transducers, for example CMUTs
• CMUTs 604 may in some embodiments be manufactured on a flexible substrate and thus in some embodiments the sensor 104 comprises a ring of ultrasound transducers 604 around the catheter 103 configured to determine the cross section of the upper airway at a number of directions. It would be understood that the ultrasound transducer(s) 604 would be impedance matched to the medium (typically air in the upper airways) to enable optimal out coupling of the acoustical waves.
• the senor 104 may be implemented by an optical sensor that fulfills the requirements above.
• the optical sensor as described herein may be configured to comprise an optical element that generates a light pattern (for example a light ring), one or more reflective elements (for example reflective cones) to direct the light pattern and/or the field of view (FOV) of the imaging device (for example a camera) to the catheter sides (it would be understood that in some embodiments the reflective element may be integrated into the light pattern generating element), an imaging device (for example a miniature camera with a large field of view).
• a light pattern for example a light ring
• one or more reflective elements for example reflective cones
• FOV field of view
• the imaging device for example a camera
• the optical element configured to generate the light pattern is connected to a laser diode via an optical fiber.
• a laser diode may be incorporated inside the sensor.
• This example thus makes use of a structured light source. Rather than generating blanket illumination, a beam of a desired shape, such as an annular ring is formed. This enables a specific line of illumination to be formed on the inner wall. This can be used for distance measurement in order to reconstruct an image of the shape of the inner wall at that location.
• the structure light source may comprise a laser diode.
• An imaging means or device such as a small camera 713, which is shown in Figure 8 located outside of the capillary 704, is aligned substantially in the same direction as the light beam 705. It is configured with a field of view 711 which is directed generally along the same direction as the light beam, i.e. parallel to the catheter axis and accordingly parallel to a general elongate axis of the optical sensor.
• the camera has a field of view which is directed generally along this direction, namely it has a central axis substantially parallel to the catheter elongate direction.
• the image generated by the imaging device or camera 713 can be furthermore configured to pass the image data to the data processing unit 401.
• the data processing unit 401 having received the image data, and with the determined geometric relationship between the optical element (the lens 703), the reflective element (the reflective cone 707) and the imaging device (the camera 713 and the camera field of view 711) can be configured to analyze the captured image data and the ring pattern to determine (or reconstruct or generate) the airway cross section dimensions.
• FIG. 9 a cross sectional view of a second example optical sensor is shown.
• the second example optical sensor differs from the first example optical sensor in that the imaging device or camera 813 is located within the transparent capillary or glass tube 804 which enables the diameter of the sensor to be reduced and produces an image without 'blind areas' on the other side of the catheter 103 to the location of the imaging device (in other words does not require the catheter 103 to be orientated in a defined or specific direction to prevent shadowing of the imaging device by the catheter).
• the optical sensor as shown in Figure 9 is located within a transparent capillary or glass tube 804 within the catheter 103. Furthermore the optical sensor comprises an optical fiber 802 which is configured to transmit a light beam to a gradient index (GRIN) lens 803 located at the fiber end.
• the GRIN lens 803 (or any other suitable lens configuration) is configured to produce a light beam (laser beam) which is projected within (and generally in the direction along) the glass tube 804 onto a surface of a reflective cone 807 also within the glass tube 804.
• the reflective cone 807 is configured to reflect the light such that it passes through the glass tube 804 wall and generates a ring pattern 809 which projected onto the airway wall 100.
• An imaging means or device such as a small camera 813 which is shown in Figure 9 located within the glass tube 804 is aligned substantially in the opposite direction as the path of the light beam. It is again configured with a field of view 811 and enabled to capture an image comprising the projection of the ring pattern 809 on the airway wall 100.
• the image generated by the imaging device or camera 813 can be furthermore configured to pass the image data to the data processing unit 401.
• the first and second examples of optical sensors as shown herein with respect to Figures 8 and 9 can be considered to be 'forward looking sensors' in that the imaging devices are generally in alignment with the catheter 103 and therefore in alignment with the transparent capillary or glass tube arrangement. They both use a reflecting cone to redirect the pattern generation light from an axial direction to a radial direction.
• An optical cone 817 is again provided, but it comprises a transparent material having a higher refractive index than the surroundings.
• the incident light 821 directed along the catheter axis direction is provided to the base of the cone (perpendicular to the catheter axis direction). The light experiences no refraction as the air to cone interface is
• the light then experiences total internal reflection at the internal cone to air boundary defined by the tapered conical face. This is because the cone angle and refractive index of the cone material are chosen to give rise to total internal reflection at the conical internal face. After reflection, the light passes to a radially opposite part of the internal cone face, with an incident angle closer to the normal. The light then exits the cone, in a direction (after a refraction at the interface which bends the light away from the normal) which is at 90 degrees to the original incident direction. This 90 degree angle is not essential, and the exit direction may instead not be perfectly radial.
• the incident light 821 is for example again received from a graded refractive index lens at the cleaved facet end of an optical fiber.
• This lens may have a width of around 0.25mm.
• the reflected light has an angle of incidence on the second face (with respect to the normal) of 3a-90 degrees. This is shown diagrammatically in Figure 10.
• the exit angle needs to be angle a for the exit light to be perpendicular to the angle of incidence.
• -sina ncos(3a).
• PMMA has a refractive index of 1.49.
• Other transparent polymers or glasses may be used, with typical refractive indices in the range 1.3 to 1.6.
• the glass tube or transparent capillary is in some embodiments connected on both sides to the (opaque) flexible catheter parts.
• the cables or connections carrying the image data generated by the imaging device (the camera) and the optical fiber can be contained.
• the optical fiber is in some embodiments coupled or connected to a laser diode configured to generate visible light, while the 'camera cable' is in some embodiments configured to couple the imaging device (camera) and the data processing unit 401.
• the airway wall distance 905 from the optical axis may be determined according to the expression:
• the airway wall distance may be determined according to any suitable manner.
• the airway wall distance can be determined by the number of imaging pixels between the ring and the camera or imaging device's optical center for a camera with a fixed field of view and zoom setting.
• FIG. 12 a cross sectional view of a third example optical sensor is shown.
• the third example optical sensor differs from the first two example optical sensors in that the imaging device or camera 811 is coupled to a second reflective element configured to convert the 'forward looking sensor' into a 'sideways looking sensor'.
• This design thus has first and second reflective elements which are back-to back with their reflecting surfaces facing outwardly.
• the use of two reflective elements enables triangulation to be used to measure the radial distance.
• the axial spacing between the two reflectors is the base of a triangle.
• the optical sensor as shown in Figure 12 is located within a transparent capillary or glass tube 1004 within the catheter 103. Furthermore the optical sensor comprises an optical fiber which is configured to transmit a light beam to a gradient index (GRIN) lens 1003 located at the fiber end.
• the GRIN lens 1003 (or any other suitable lens configuration) is configured to produce a light beam (laser beam) 1105 which is projected within (and generally in the direction along) the glass tube 1004 onto a surface of a reflective cone 1007 also within the glass tube 1004.
• the reflective cone 1007 is configured to reflect the light such that it passes through the glass tube 1004 wall and generates a ring pattern 1009 which projected onto the airway wall 100.
• An imaging means or device such as a small camera 1013 which is shown in Figure 12 located within the glass tube 1004 and is aligned substantially in the opposite direction as the path of the light beam is configured with a field of view 11 11 defined by the second reflective cone 1012 and enabled to capture an image comprising the projection of the ring pattern 1009 on the airway wall 100.
• the image generated by the imaging device or camera 1013 can be furthermore configured to pass the image data to the data processing unit 401.
• Figure 13 two versions of 'sideway- looking' optical sensor configurations are shown.
• the 'hybrid' sensor in some embodiments has certain advantages over both the 'forward facing sensor' and the 'sideways facing sensor configurations'.
• the light beam 1105 deflected by the first reflective element of reflective cone 1107 generates the ring pattern 1109 on the airway way.
• the deflected field of view as described herein can be used to detect there the airway wall is relatively far from the sensor and the non-deflected field of view can be configured to detect when the airway wall is very close to the sensor.
• the configuration of the imaging device (camera 1113) and the second reflective element or reflective cone 1112 can be arranged so that there is an overlap in coverage between the reflected FOV and the direct FOV regions.
• This overlap in coverage can be configured for the corners of the camera image where the FOV of the camera is largest.
• this 'double' ring determination can be used as an error indicator to detect when the sensor is too covered or obscured by secretions to work properly.
• a cross sectional view of a fourth example optical sensor is shown.
• the fourth example optical sensor differs from the third example optical sensor in that the lensing element and reflective elements are generated from air gaps within a molded plastic (or other machined transparent material) rod rather than using GRIN lenses and reflective elements inserted into a glass tube or transparent capillary.
• the fourth example optical sensor is therefore cheaper and easier to manufacture, needing fewer components to be aligned perfectly.
• implanting such sensors the illumination or light beam passes through fewer interfaces and therefore produces fewer parasitic refiections.
• the 'solid' sensor as shown in Figure 14 comprises two elements which are molded, machined or cut glass or plastic rods 1215 butted together as shown by joins 1206.
• the first glass or plastic rod comprises two air-filled cavities or hollows 1296, each of which defines an optical component.
• the first hollow defines a first lens shape 1203 and is configured to receive the fiber 1202 via a fiber pigtail 1299.
• the second hollow defines a first reflective element or cone shape 1207, configured to reflect the light beam to generate the ring pattern 1209 projected onto the airway wall.
• the second glass or plastic rod comprises a second reflective element or cone shape hollow 1212 for reflecting the imaging device (or camera 1213) field of view.
• the refractive index of the rod and the cone angle are suitable, then total internal reflection occurs at the cone-air boundary and the cone-shaped cut functions like a reflective cone. Alternatively in some embodiments an additional reflection layer is applied to produce the reflective surface.
• the imaging device or camera 1213 can be located or aligned within the sensor by the second glass or plastic rod having a imaging device or camera bore, hollow or hole within which the camera is fitted.
• the imaging device is configured with a field of view 1211 defined by the a second reflective element or cone shape hollow 1212 to capture an image comprising the projection of the ring pattern 1209 on the airway wall.
• the image generated by the imaging device or camera 1213 can be furthermore configured to pass the image data to the data processing unit 401.
• the solid sensor as discussed herein comprises of two solid rods of transparent glass or plastic which are glued together, using any suitable glue, at joins 1206.
• the rods are scored or grooved.
• the light ring projected onto the airway wall is a substantially whole ring.
• the light pattern projected can be more sophisticated than a simple ring.
• the light pattern can provide a better or more robust reconstruction of the airway.
• a light pattern is generated by implementing or employing a Diffractive optical element (DOEs) plate or foil.
• DOEs Diffractive optical element
• a custom made DOEs can in such embodiments produce nearly arbitrary diffraction patterns in the transmitted beam.
• a sensor can be configured with a DOE foil or grid 1311 located between the GRIN lens and the reflective cone.
• a DOE foil or grid 1313 can be located around the cone reflective cone, such as shown in the right hand side of Figure 15.
• the DOE shown in this example creates 3 concentric rings. The additional rings can in such embodiments be used to improve the precision with which the distance to airway walls can be measured.
• DOE foil or grid could furthermore be incorporated within the 'forwards looking sensor' or 'solid sensor' examples as discussed herein.
• a holographic element for example a holographic crystal or a holographic polymer element
• a holographic element can be employed to creates a holographic (or complex) light pattern when illuminated.
• the reflective elements were described as straight cones, in other words the reflective surface is linear. In some embodiments however the reflective surface can be non- straight (or in other words
• a sensor comprising a reflective cone 1412 to reflect the imaging device or camera 1413 field of view which is configured to have a curved reflective surface.
• the field of view 1423 of the sensor is usually limited to the field of view 1421 of the camera, however by employing a reflective cone with concave side, it is possible to increase the sensor field of view and produce the same effect as adding a concave lens, but without the additional cost and alignment issue.
• the concave reflective cone shape can be implemented with respect to the reflective cones according to 'forwards looking sensor', 'sideways looking sensor' or either implementations of the 'solid sensor' embodiments.
• a curved cone could be implemented in order to replace the GRIN (or other) lens for generating the beam for providing the projected ring.
• the reflective elements or reflective cones can comprise step-wise straight sides but with different angles. For example by implementing a step-wise reflective surface with different angles as the light beam reflective element a more
• the light from the GRIN lens 1503 is reflected by the stepped cone with two angles 1507 to produce a light pattern of two rings.
• Reflective cone 1512 is correspondingly chosen having appropriate geometric properties to provide a projected camera 1513 field of view wide enough to capture all generated ring patterns.
• a coverage overlap area can be created enabling an error detection operation as discussed herein.
• the camera 1513 and GRIN lens 1503 are arranged in the same radial plane, offset from each other.
• the camera has a field of view with a central axis aligned with the catheter central axis, and the camera cone 1512 is accordingly also centered on the catheter central axis.
• the light dispersing cone 1507 also received incident light parallel to the catheter elongate axis, but offset from the central axis.
• the camera cone 1512 and the light dispersing cone face in the same longitudinal direction.
• this is achieved by employing a light dispersing cone 1507 of a size very much smaller than the respective camera cone 1512, and by mounting said light dispersing cone at a point radially displaced from the center of the catheter, outside of the field of view of the camera 1513.
• Light is propagated from GRIN lens 1503 toward the surface of the light reflecting cone 1507.
• the light reflecting cone has surface adapted to reflect all incident light such that it exits the catheter at a perpendicular (i.e. radial) angle with respect to the catheter longitudinal axis.
• the reflected radial beam projects ring pattern 1509 at the surrounding airway walls.
• the light dispersing cone 1507 reflects light perpendicularly, its off- center position has no effect on the radial symmetry of the generated ring pattern 1509. This would be in contrast, for example, to a cone adapted to reflect light at a range of angles, wherein an off-center positioning would generate a ring pattern having differing widths at different points about the circumference of the airway,
• the light reflecting cone 1507 may be adapted to produce radial propagation by, for example, employing a conical surface with an inclination of 45 degrees with respect to the longitudinal axis of the catheter, in combination with incident propagation vector from the GRIN lens 1503 substantially parallel with said axis. With this arrangement, light incident from the lens reflects from the 45 degree cone surface at an angle normal to the surface of the catheter (i.e. in a radial direction).
• camera cone 1512 projects an image of a ringed section of the airway, defined by sensor field of view 1523, and illuminated by ring pattern 1509, into the (horizontal) camera 1513 field of view.
• the generated sensor field of view 1523 is ideally wide enough to encompass ring pattern 1509, while narrow enough to exclude capturing light dispersing cone 1507.
• the camera cone 1512 in some examples of this embodiment may have surface inclination angle at the apex of approximately 126 degrees. At this angle, the cone is for example able to project images to the camera 1513 from surfaces which are at a radial distance of between 0.32 and 29.7 mm from the outer perimeter of the catheter 103. This is based on a catheter outer diameter of 3mm, and is the range of radial distances for which the projected field of view 1523 overlaps with the ring pattern 1509.
• the rigid sensor section of the catheter is this example may have length of approximately 10mm.
• the camera 1513 (as an optional feature) has a field of view which is wide enough to capture light from further in front. This enables contour mapping using distance measurement based on the ring pattern, and also
• the light reflecting cone 1507 may be a specular surface-reflecting cone (e.g. aluminum) or it may be a total internal reflecting cone (with the tip facing the opposite direction) as explained above with reference to Figure 10.
• the imaging system may instead be off center, or indeed both units may be off center. Different designs will give different ways of using the available space.
• each optical sensor may have a sensor length up to 45 degrees offset from the catheter direction with an image sensor having a field of view with a central axis with up to this 45 degree offset.
• the angle is less than 30 degrees or less than 20 degrees.
• the purpose may be to create a non-perpendicular image slice. This will be the case if the image sensor reflector provides a 90 degree reflection, so that the image slice is non-perpendicular, and the reflected received light is then off-axis.
• the internal sensor components may be rotated.
• the local area around the sensor may be scanned by rotating the catheter. This might also be a way to find the orientation in which the illumination ring is indeed (almost) perpendicular to the centerline.
• the additional freedom can also be used to adapt to the local anatomy, As an example the uvula blocks part of the illumination ring for a range of perpendicular cross sections. Introducing an angle enables the illumination ring to extend to the opposite side of the airway past the uvula.
• a deliberate tilt may be desired in the anterior-posterior direction or in the lateral directions.
• Figure 19 a second or further configuration of sensor arrangement on the catheter is shown.
• the catheter 1603 comprises a multitude of sensors 10413 distributed along the catheter 1603 so that the whole length of interest is covered with sensors 10413.
• the spacing of the sensors 10413 may be chosen in such a way that the spacing is small enough to get a representative representation of the airway regardless of the size of the airway.
• the data processing unit 401 may be configured to interpolate the cross sections at a given position in the airway which is not directly covered by a sensor 104 ⁇ by interpolating neighboring sensor cross sections.
• the catheter 1703 is configured with sensors 104 5 , 104 7 ,
• the catheter 1703 comprises a downward looking sensor 10415 in the tip of the catheter that specially monitors the epiglottis 5.
• the catheter 1703 in such embodiments would therefore be a shorter catheter ending just before the epiglottis 5.
• the 'epiglottis' sensor 10415 may comprise a light pattern generating element with a defined light pattern 1701 and an imaging device, such as a camera for imaging the epiglottis under the light pattern.
• the 'epiglottis' sensor 10415 may be a 2-dimensional array of ultrasound transducers configured to produce a 'view' of the epiglottis from the tip or end of the catheter 1703.
• the catheter sensor configuration is such that there is in such
• At least one sensor located at the distal end of the catheter configured to observe or measure the volume (such as the airway as discussed herein) adjacent the distal end of the catheter as well as at least two sensors distributed spaced along the catheter.
• Figure 20 shows a sensor arrangement or configuration similar to the first example, such as shown in Figure 4 but with the 'epiglottis' sensor it would be understood that the sensor arrangement or configuration may be similar to the second example, such as shown in Figure 19 with the end sensor replaced with the 'epiglottis' sensor.
• the examples above make use of a structured light source for each imaging system, in order to create a line of illumination (or a more complicated pattern of illumination) on the inner surface of the volume being imaged.
• the relative complexity of a structured light generation unit contributes to the cost of the overall device.
• the catheter for upper should be a one-time, disposable product.
• Figure 21 shows a simplified version without using relatively expensive structured light. Instead the catheter employs cameras 2103 with embedded light sources, which are available on the market.
• Two cameras 2103 are arranged as one forward looking and one backward looking camera. They provide blanket non-structured illumination with an output which basically corresponds to the field of view of the camera.
• the illumination envelope and the field of view of the camera are thus both represented by reference 2105.
• the cameras 2013 are inside the catheter 103.
• the illumination direction and central axis of the field of view are aligned with the catheter direction, but with a radial extent so that the inner wall of the tube 100 is illuminated and imaged.
• the cameras have a wide viewing angle for this purpose. They are contained within the flexible and transparent catheter tube 103.
• the cameras contain embedded LED illumination units such that the camera can record the portions of the upper airway of interest.
• the light generator is thus an integral part of the imaging device, and generates a non- patterned light output.
• the distance between the cameras 2013 is known. Since the cameras simultaneously record upper airway dynamics from opposite directions, the evolution of upper airway narrowing can be better followed compared to the situation of cameras looking in the same direction parallel to the catheter. Based on the relative movement of structures and the difference between what is shown by the two cameras, spatial information can be derived about the location of narrowing.
• the device as described above in all the different examples is for obtaining images or distance profiles at a set of positions.
• the catheter may be accurately positioned so that specific areas of interest are imaged.
• the catheter may be anchored in position in known manner to ensure the correct position is maintained.
• the optical sensor is described with respect to a medical catheter.
• the optical sensor can be implemented within and along any suitable sensor array configuration for monitoring cross sectional regions or pipes, conduits of any suitable shape or size.
• the optical sensor can in some embodiments be implemented within a sensor array deployed within a volume for the observation or checking of cross-sectional consistency.
• the optical sensors can provide an indication of the location of any collapse or constriction.

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